Method of finishing end edges of plasterboard



p 1950 G. A. BUTTRESS 2,523,861

METHOD OF FI NISHING END EDGES 0F PLASTER BOARD Filed April 2, 1946Patented Sept. 26, 1950 UNITED METHOD OF FINISHING END EDGES FPLASTERBOABD George A. Buttress, Los Angeles; Calif.

Application April 2, 1946,'Serial No. 658,952

2 Claims. (Cl. 154-87) This invention relates to plaster board of thetype wherein a sheet-like body or filler of hardened plastic material isfaced with card-' board or similar sheets to produce a board for use asa base for plaster on walls and ceilings or as sheeting in finishingwalls and ceilings, and more particularl pertains to th finishing ofsuch board so that critical margins of the plastic sheet-like body arecovered by the facing sheets and the board is given a particular shapeand finished appearance along margins thereof to provide advantageswhich will be hereinafter pointed out.

In the manufacture of plaster board, cardboard or like facing sheets arefed in long strips over a table or on a conveyor while a soft and wetplastic material is applied therebetween whereby a long strip of plasterboard stock may be formed subject to being cut into desired lengths whenthe plastic material has set. Later methods provide for bending orfolding the facing sheets around the longitudinal edges of the longstrip of stock board during the forming thereof so that the plasterboard lengths cut from the strip will have certain opposite edgesthereof in finished and protected form with the plastic body sheetcovered along said edges by the cardboard facing sheets. However, in sofar as I am aware, the transverse edges of these board lengths aresquare, expose the dry plastic filler and present an unfinishedappearance. Exposure of the dry plastic body sheet in this manner isobjectionable in that when plaster is applied over a number of suchboards or a wall or ceiling, the exposed edges of the dry plastic bodysheet will absorb moisture from the applied plaster at the joints ofsaid boards and weaken the plaster at the most critical points, namely,the joints in the base formed by the boards, thereby impairing themonolithic characteristic of the body of applied plaster'and oftencausing cracking and discoloration thereof. Moreover, these ordinarysquarecut edges of the board when opposed in an assembly of plasterboards on a wall or ceiling donot afford an eliective keying of theapplied plaster and present an unfinished appearance especially when theboards are used as finishing sheeting on walls and ceilings.

It is the primary object of this invention to provide a method and anapparatus for producing finished, cardboard-covered edges of boardlengths of plaster board of the character described, incident to thesevering of such lengths from a long strip of the plastic board stockwith the edges produced by such severing given a particular shape andtreatment to facilitate the keying of plaster applied to a plurality ofthe boards,

-give the boards, finished appearance, and reinforce and add to thestrength thereto.

Another object of this invention is to provide a method of finishingplaster board of the character described while the cardboard facingsheets and the plastic filler thereof are yet wet as before the settingof the latter, which consists in first applying to the facing sheetsalong a line extending across both sides of the board, a pressure suchthat the plastic filler will be laterally displaced and the facingsheets forced inwardly and caused to form grooves and to adhere to oneanother along the bottoms of said grooves, and then forcibly continuingthe pressure in such manner that the adhered portions of the facingsheets are severed, whereby successive applications of the aforesaidpressures at spaced points along the plaster board stock will producedesired lengths of plaster board each having the plastic body along thesevered edges covered by the adhering portions of the facing sheets andbeing given a predetermined beveled or tapered form at such edges.

Another object is to provide a finishing apparatus for plaster boardwherein opposed dies are first pressed against opposite sides of the wetunhardened stock length of plaster board to form transverse grooves inopposite sides of the board with the cardboard facing sheets forcedtogether and adhered to one another along the bottoms of said grooves,and then forcibly moved toward one another so as to sever the facingsheets along the adhering portions thereof whereby the result ant edgesare sealed by said adhered portions of such sheets and are beveled onopposite sides and given a finished appearance.

With the foregoing objects in view, together with such other objects andadvantages as may subsequently appear, the invention resides in theparts and in the combination, construction and arrangement of partshereinafter described and claimed, and illustrated by way of example inthe accompanying drawing, in which:

Fig. l is a fragmentary side elevation of an apparatus embodying thepresent invention and constituting one means by which the method hereofmay be carried out, the apparatus being shown in readiness foroperation;

Fig. 2 is a sectional view taken on the plane of line 2-2 of Fig. 1,showing in cross section the apparatus of Fig. 1 and in addition theconfining elements which extend along the longitudinal appear during thefinishing operation but before.

the facing sheets and the stock" have been severed;

Fig. 4 is asectional view similar to Fig. 3 showing the die members andboard as when a severing operation has been completed; and

Fig. 5 is a fragmentary side elevation of a finished plaster board asproduced with the method and apparatus hereof.

The method of this invention is-preferably carried out inconnection-with plaster board which in being formed in long stock stripssubject to having suitable lengths or pieces cut therefrom has itslongitudinal edges covered by one or both of the cardboard facingsheets, so that the plastic body sheet of the board is sealed-in andcovered along such edges before it sets. This arrangement protects thelongitudinal edges of the plaster body sheet to which the cardboardfacing sheets are adhered and prevents exposure of the plastic materialat the longitudinal margins of the board and consequent objectionableabsorption of moisture from plaster applied over such edges. However,the method hereof may be carried out to advantage with plaster board inwhich the plastic body is exposed along the longitudinal edges of theboard, inasmuch as the other edges of the plastic body produced incutting of lengths of board will be covered and finished in accordancewith invention and .to that extent the product will be considerablyimproved as compared to board in which all the margins of the plasticbody are exposed.

In carrying out the method hereof, a length of plaster board stock A innearly complete form, that is, after the plastic filler B has beenapplied between the cardboard facing sheets C and the assembly has beenpressed into substantially its finished sheet or board form and beforethe plastic material has set and while the facing sheets are still wetor damp, is subjected to pressure on opposite sides along a lineextending transversely thereof as by means of opposed die members D andE so as to press portions of the facing sheets toward one another andsqueeze and displace the soft plastic material laterally until a grooveof a somewhat arcuate cross section is formed to extend across in eachside of the board, and the pressed-in portions of the facing sheets abutand adhere to one another along the bottoms of said grooves. The boardnow appears as shown in Fig. 3 with adhering portions of the facingsheets substantially equal in width to that of the bottoms of saidgrooves.

The next step in the method hereof consists in continuing the pressureso that it is forcefully applied in such manner along the longitudinalmedial lines of the portions of the facing sheets which are adhered toone another, that said adhering portions will be severed along saidmedial lines. This parting or severing operation produces like sealedand finished edges as shown in Fig. 4, with the plastic filler sealed-inalong such edges by the lip-like portions of the facing sheets whichremain adhered to one another on opposite sides of the line on whichsuch sheets are severed.

Upon repeating these method steps at another point longitudinally spacedfrom the first finishing and severing point, there will be produced afinished plaster board of desired dimensions and on which the edgesformed in severing the board as aforesaid, will be beveled on oppositesides with the plastic filler covered and sealed-in by the portions ofthe facing sheets which adhere to one another. Thus produced the cut-offlengths of plaster board are ready for use when the plastic filler setsand the facing sheets are dried out in any suitable manner.

It should be noted that due to the cardboard sheets being damp or Wetand the plastic material being soft when the forming and severingoperations hereof are performed, and the manner in which the pressure isapplied to form grooves in the board then sever it along thelongitudinal center lines of the grooves, the cardboard portions areconverted at the severed edges and adhered to one another and remain incontinuity with the facing sheets propen'with the plastic materialcompressed, increased in density and therefore strengthened at saidedges. It should be noted that at least one of the sealed lengths ofboard being formed by this methodis maintained under pressure andconfined between the table I and the pressure plate 8 as well as-betweenthe side retaining members ll, while having a transverse edge thereofsealed and cut, thus maintaining the board length in uniform fiatformation free from bulges or deformations which would otherwise occurdue to displacement of the plaster when forming the sealed transverseedges.

Apparatus embodying the present invention as her shown includes asupport I such as a table or the like adapted to support the stocklength A of plaster board which is to be cut into smaller pieces orlengths to form a plurality of plaster boards.

The dies D and E hereinbefore referred to, for forming and severing theboard A are disposed above and below the upper surface of the table 1respectively, in superposed relation for movement towards and away fromone another. The die D is supported on a transverse edge of a pressureplate 8 which is normally disposed above and clear of the stock length Aof plaster board whereas the die E is mounted on a plate or support 9disposed below the table and adapted to be moved through a transverseslot I 0 in the table into contact with the underside of the board atthe same time that die D is moved into contact with the upper side ofthe board.

Any suitable means, not shown, may be employed for moving the plates 8and 9 so that the dies D and E will be forcibly engaged with the board Ato first form the groove in opposite sides thereof, cause the facingsheet C to adhere to one another as shown in Fig. 3; and then sever saidadhering sheets and finally be moved back into out-of-the-way positionshown in Figs. 1 and 2.

As here shown retaining members II are mounted along opposite sides ofthe table I so that when the dies D and E are moved into forming andsevering positions, the board A will be confined under pressure and heldagainst displacement and deformation by means of the plate 8, table Iand side members I I, except where the dies are contacted therewith.

The dies D and E are of such length as to extend fully across the boardA and have the edges thereof opposed to the board A, of specialformation so that when forced against oppositesides of the board theywill form the like grooves C of arcuate cross section and cause thefacing sheets to abut and adhere to one another before being severed. Ashere shown said opposed edges of the dies are provided with likeslightly concaved or inwardly curved faces l2 converging so as to formsomewhat rounded ridge-like severing edges 13. This shape of the dies issuch that the edges of the finished board provided by the severingoperation will be somewhat rounded and the portions of the facing sheetswhich cover said edges will form a small protruding lip where adhered toone another along such edges.

The roundingpof the severing edges 13 of the dies assures that theaforesaid shaping and adhering operations will take place beforesevering the facing sheets on the longitudinal center line of theadhering portions, the object being to prevent the severing operationfrom taking place before the plastic material while yet soft isdisplaced, compressed and given a definite form and the two sheets arebrought into abutting relation and caused to adhere to one another.

It will now be apparent that upon successive applications of the dies Dand E and hereinbefore noted at spaced intervals along the length ofplaster board stock A before the plastic filler B has set, there may beprovided in an eflicacious manner a plurality of plaster boards in whichthe edges formed by such applications of the dies are covered byintegral portions of the facing sheets so as to seal in the plastic'filler B and give a shape to such edges affording a better keyingaction when plaster is applied to such boards as well as reinforcingsuch boards and providing the other advantages herein noted in aparticularly efllcacious manner.

This invention embraces a new form of plaster board wherein the severededges are given a particular form and are sealed by portions of thefacing sheets.

While I have shown and described a specific embodiment of my invention,I do not limit myself to the exact details of construction set forth,and the invention embraces such changes, modifications and equivalentsof the parts and their formation and arrangement as come within thepurview of the appended claims.

I claim:

1. The method of finishing edges of plaster board before setting andhardening of the plastic body of such board and to which body cardboardfacing sheets are adhered; which consists in pressing inwardly opposedportions of the facing sheets of a stock length of such board so as todisplace the plastic body and cause said pressed-in portions of saidsheets to abut and adhere to one another along a line extendingtransversely of said board, restraining the entire area of oppositesides and the longitudinal edges of a given length of the board duringthe pressing of said sheets into abutting relation, to preventdeformation of such given length of board incident to said displacementof said plastic body, then severing said adhering portions along a linewhich is intermediate the side edges of said adhering portions wherebythe edges of the plastic body formed by such severing will be coveredand sealed by portions of said facing sheets which are adhered to oneanother along said edges.

2. The method of producing finished edges of plaster board which edgesare produced in severing given lengths of plaster board from a stocklength of such board; which consists in pressing and confining againstdisplacement the entire area of opposite sides and the longitudinaledges of a given length of the board while pressing in- REFERENCES CITEDThe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 700,805 Paine May 2'7, 19021,353,524 Fleming et a1 Sept. 21, 1920 1,417,117 Tyler May 23, 19221,464,360 Hicks Aug. '7, 1923 1,874,922 Delaney Aug. 30, 1932 1,884,708Jeneson Oct. 25, 1932 1,949,692 Pavesi Mar. 6, 1934 2,134,862 DunnamNov. 1, 1938 2,142,505 Gammeter Jan. 3, 1939 2,168,803 Page Aug. 8, 1939

